The court ruled that the identity of the witness — an alleged survivor of a church arson attack — should not be revealed for safety reasons. She will be referred to by the number 536, according to the BBC.

Chief prosecutor Fatou Bensouda has previously said that witnesses have been intimidated in an attempt to prevent them from testifying.

Some 1,200 people were killed and 600,000 more forced from their homes in weeks of violence after the election. Six years later, more than 40,000 survivors are living in camps.

Prosecutor Anton Steynberg told the court that "22 victims and witnesses, common Kenyan people, who will describe the attacks" would be called to testify at Ruto's trial, Kenya's Daily Nation newspaper reports.

Ruto, head of a Kalenjin-language radio station, is accused of fomenting ethnic hatred, a charge that he denies.

The first prosecution witness was a victim of an arson attack in January 2008 on the Kiambaa church in Naivasha, a town in Kenya's Rift Valley.

A mob set ablaze the church where people were taking refuge, burning 44 people beyond recognition.

The violence erupted after the opposition claimed that it had been robbed of victory. It then took on ethnic overtones, with Kenya's main groups — especially Kikuyus and Kalenjins — involved in attacks and reprisals.